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More than 15,000 people have been forced to evacuate

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Soldiers are helping to clear debris from the roads

More than 15,000 people have had to evacuate their homes, with more expected in the coming days.

"I must emphasise that this is just the start. People must remain alert while we try to pick up the pieces in areas already hit," said Alexander Pama, head of the government's main disaster agency, quoted by AFP.

A teenage boy was killed and four other people injured in Manila, when a tree toppled onto houses.

Rescuers saw two bodies floating in floodwater in northern Nueva Ecija, one of the worst-hit states, but it has not been confirmed if they died because of the typhoon.

Flights and ferry services in the north have been cancelled and some bus services in mountain areas suspended due to the threat of landslides.

On Friday, President Benigno Aquino made a televised warning, the first time he had done so since Super Typhoon Haiyan in 2013, which killed more than 6,300 people.

BBC science editor David Shukman, who is in the capital Manila, says public warning systems have been greatly improved since Typhoon Haiyan, so there is a much better chance of keeping people safe.

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Media captionNorthern Luzon resident Damon Simms: ''I've had to batten down the hatches''

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Media captionThis powerful storm has hit the Philippines bringing damaging winds and huge waves; but it's the rainfall which could bring the most problems, as Helen Willetts explains.

Typhoon Koppu, also known as Lando, is up to 650 km (404 miles) across.

Speaking in Manila, Lotta Sylwander of Unicef told the BBC that people in the worst hit areas needed to be able to sustain themselves for up to 72 hours.

"That's how long the typhoon is going to take to pass and during that time it's going to be extremely difficult to come in with any kind of transport," she said.

"We're hoping that people really did prepare and have enough food and water at home."

Why is Koppu slow-moving? Chris Fawkes, BBC Weather Centre, explains:

There are two typhoons in the west Pacific at the moment - Typhoon Champi sits just to the east of Koppu.

The complex interaction between these two typhoons and the warm air within these storms helps to build a ridge of high pressure over Taiwan this weekend. It is this ridge that effectively traps typhoon Koppu over the Philippines for a number of days rather than it being able to turn away from the Philippines and out of harm's way to the South China Sea.

Some computer models suggest the storm system will still be affecting the Philippines into the middle of next week allowing colossal amounts of rain to accumulate - 1m (39in) of rain is possible. Such extreme rainfall would bring some severe flooding to Luzon.

"No power anywhere in Nueva Ecija. Nothing to see beyond the windows but pitch blackness," he told the BBC in an email.

In his televised appeal on Friday, President Aquino urged the estimated six million people in the typhoon's direct path to listen to government warnings and be ready to evacuate their homes if necessary.

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The typhoon whipped up coastal surges

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But this bride's wedding still went ahead

He said aid agencies had already distributed emergency supplies to evacuation centres.

"Your government is here to help us achieve zero casualties," Mr Aquino said.

Meanwhile, the Philippine military in northern Luzon has been placed on alert for disaster operations.

Typhoon Koppu is not due to leave the Philippines until Tuesday, when it will be heading towards Taiwan.